Double Star System Detected Using New South African Radio Telescope
May 16, 2013

Double Star System Detected Using New South African Radio Telescope

Lee Rannals for — Your Universe Online

Astronomers using the Karoo Array Telescope (KAT-7) in South Africa have revealed giant outbursts from X-ray binary star system Circinus X-1.

The team watched as the double star system fired off energetic matter from its core into the surrounding system in extensive, compact jets that flared brightly. Circinus X-1 is a neutron star system where the two stars orbit each other every 16.5 days in an elliptical orbit. When the two stars are at their closest the gravity of the dense neutron star pulls material from the companion star, causing a powerful jet of material to blast out of the system.

Astronomers used KAT-7 to observe as the system flared twice at levels among the highest ever seen. They said this was the first time the system has been observed with such detail.

"One way of explaining what is happening is that the compact neutron star gobbles up parts of its companion star and then fires much of this matter back out again," explains Dr Richard Armstrong, an SKA SA Fellow at the University of Cape Town and lead author of the paper published in the journal Monthly Notices of the Royal Astronomical Society. "The dramatic radio flares happen when the matter Circinus X-1 has violently ejected slows down as it smashes into the surrounding medium."

Professor Rob Fender, Head of the Astronomy Research Group at the University of Southampton, said the star system provides one of the best opportunities for astronomers in the sky.

"Circinus X-1 continues to reveal new aspects of its behavior, and is arguably the best laboratory for relativistic jet astrophysics in the southern hemisphere," Fender said. "It is furthermore an excellent control to the large population of jets associated with accreting black holes."

Armstrong said these types of observations of binary star systems are crucial for understanding the processes of accretion of matter onto extremely dense systems.

In April astronomers using NASA's Kepler space telescope observed the effects of a dead star in a double star system bending the light of its companion star. This was one of the first detections of this type in a binary system. At first the team thought Kepler picked up a gas giant circling its star, but later they discovered that it was actually a white dwarf with a burnt-out core.